PMID- 12830341
OWN - NLM
STAT- MEDLINE
DCOM- 20040105
LR  - 20181113
IS  - 0014-4819 (Print)
IS  - 0014-4819 (Linking)
VI  - 151
IP  - 4
DP  - 2003 Aug
TI  - Further evidence to support different mechanisms underlying intracortical 
      inhibition of the motor cortex.
PG  - 427-34
AB  - Paired-pulse magnetic stimulation has been widely used to study intracortical 
      inhibition of the motor cortex. Inhibition at interstimulus intervals (ISIs) of 
      1-5 ms is ascribed to a GABAergic inhibitory system in the motor cortex. However, 
      Fisher et al. have proposed that different mechanisms are operating at an ISI of 
      1 ms and 2.5 ms. In order to confirm their concept and clarify whether inhibition 
      at all these intervals is produced by a single mechanism, we compared effects of 
      paired-pulse stimulation at ISIs of 1 ms, 2 ms, and 3-5 ms. We evaluated how 
      intracortical inhibition affected the I3-wave, I1-wave, magnetic D-wave, and 
      anodal D-wave components of electromyographic (EMG) responses using previously 
      reported methods. The data suggest that three separate effects occur within these 
      ISIs. At ISIs of 3-5 ms, inhibition was evoked only in responses to I3-waves, 
      whereas no inhibition was elicited in responses to I1-waves or magnetic D-waves. 
      In contrast, at an ISI of 1 ms, responses to I3-waves and I1-waves were 
      moderately suppressed. Moreover, even magnetic D-waves were slightly suppressed, 
      whereas anodal D-waves were unaffected. At an ISI of 2 ms, none of the descending 
      volleys were inhibited. We propose that we should use ISIs of 3-5 ms for 
      estimating function of the GABAergic inhibitory system of the motor cortex by 
      paired-pulse transcranial magnetic stimulation (TMS). Our results support the 
      idea of Fisher et al. that the mechanism responsible for the inhibition at an ISI 
      of 1 ms is not the same as that responsible for suppression at ISIs of 3-5 ms 
      (GABAergic inhibitory circuits in the motor cortex). At an ISI of 2 ms, we 
      suggest that the inhibitory influence evoked by the first stimulus (S1) should 
      collide with or be occluded by the second stimulus (S2), which leads to the lack 
      of inhibition when the subjects make a voluntary contraction of the target 
      muscle.
FAU - Hanajima, Ritsuko
AU  - Hanajima R
AD  - Department of Neurology, Division of Neuroscience, Graduate School of Medicine, 
      University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
FAU - Furubayashi, Toshiaki
AU  - Furubayashi T
FAU - Iwata, Nobue Kobayashi
AU  - Iwata NK
FAU - Shiio, Yasushi
AU  - Shiio Y
FAU - Okabe, Shingo
AU  - Okabe S
FAU - Kanazawa, Ichiro
AU  - Kanazawa I
FAU - Ugawa, Yoshikazu
AU  - Ugawa Y
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20030627
PL  - Germany
TA  - Exp Brain Res
JT  - Experimental brain research
JID - 0043312
RN  - 56-12-2 (gamma-Aminobutyric Acid)
SB  - IM
MH  - Adult
MH  - Cerebral Cortex/*physiology
MH  - Efferent Pathways/physiology
MH  - Electromagnetic Fields
MH  - Electromyography
MH  - Female
MH  - Humans
MH  - Interneurons/physiology
MH  - Male
MH  - Middle Aged
MH  - Motor Cortex/*physiology
MH  - Muscle Contraction/physiology
MH  - gamma-Aminobutyric Acid/physiology
EDAT- 2003/06/28 05:00
MHDA- 2004/01/06 05:00
CRDT- 2003/06/28 05:00
PHST- 2002/07/22 00:00 [received]
PHST- 2003/02/26 00:00 [accepted]
PHST- 2003/06/28 05:00 [pubmed]
PHST- 2004/01/06 05:00 [medline]
PHST- 2003/06/28 05:00 [entrez]
AID - 10.1007/s00221-003-1455-z [doi]
PST - ppublish
SO  - Exp Brain Res. 2003 Aug;151(4):427-34. doi: 10.1007/s00221-003-1455-z. Epub 2003 
      Jun 27.